✦ Small size planets orbiting solar-type stars with about 1 year period.

The exo-planets discovered by PLATO can be fully characterized

✦ The same data that PLATO acquires for the planet search, are used to derive the internal structure of the hosting stars (by means of asteroseismology techniques). This is mandatory to:

★Precisely measure properties of exoplanets: mass, radius, age

★Comparatively study planetary systems of different ages; e.g., the parameter range of super-Earths to Earth planets is basically unexplored.

★Observe exo-planets in different stages of dynamical evolution and in different stages of physicochemical evolution

★Correlate the planet and hosting star evolution.

✦ PLATO will search planets orbiting bright stars. After the planet detection, it will therefore possible to follow up the exo-planetary system with ground based and space telescopes (e.g., E-ELT, JWST, EChO, etc. ) in order to obtain a complete characterization of the planet, its atmosphere, and the whole planetary system.

Slightly less than 2000 extrasolar planets and a few thousand of planet candidates have been discovered since 1995. New discoveries are every week announced. The detection techniques used up to date have biased our results toward Jupiter-mass planets in orbits very close to the star. More recently, a number of planets of smaller mass (Neptunian-like till super-Earths) has been detected orbiting low mass stars.

Thanks to the high stability of their photometric measures, space missions, as CoRoT and Kepler have demonstrated, can easily detect transits of small planets in front of their hosting star.

We have learned that planetary systems can differ substantially from ours. But is our system special? This question still cannot be answered today, since the terrestrial planets at intermediate distances, like Mercury, Venus, Earth and Mars which characterize our Solar System, are out of reach of existing and upcoming ground- and space-based exoplanet surveys over the next decades. A true placing of the Solar System among the stars is therefore still out of reach.It is this question that PLATO will finally answer.

The Main Science Objective and the PLATO Performances according to the performed studies are given in this page.

PLATO can reach a coverage up to 42% of the sky with the required observing strategy of:

✴ Two main fields observed sequentially for 3 years/each

✴ A number of Step&Stare phases with duration between 2 and 5 months

Thanks to the large surveyed area, the number of Bright Stars investigated by PLATO 2.0 is huge with respect to previous missions.

PLATO will provide:

~85 000 stars with asteroseismology

~1 000 000 accurate lightcurves

~100 – 1000 super-Earths transits in the HZ of solar-like to cool dwarfs

Thousands of mini-Neptunes and gas giants

Moons, rings, exocomets

Ages of planetary systems

Planets around sub-giants, giants, post RGB stars, circumbinaries, …

… for had we never seen the stars, and the sun, and the heaven, none of the words which we have spoken about the universe would ever have been uttered. But now the sight of day and night, and the months and the revolutions of the years, have created number, and have given us a conception of time, and the power of enquiring about the nature of the universe…